1. Field of the Invention
The present invention is directed to a prosthetic device for repairing or replacing cartilage or cartilage-like tissues. Said prosthetic devices are useful as articular cartilage substitution material and as scaffold for regeneration of articular cartilagenous tissues.
2. Description of the Related Art
Articular cartilage tissue covers the ends of all bones that form diarthrodial joints. The resilient tissues provide the important characteristic of friction, lubrication, and wear in a joint. Furthermore, it acts as a shock absorber, distributing the load to the bones below. Without articular cartilage, stress and friction would occur to the extent that the joint would not permit motion. Articular cartilage has only a very limited capacity of regeneration. If this tissue is damaged or lost by traumatic events, or by chronic and progressive degeneration, it usually leads to painful arthrosis and decreased range of joint motion.
Several methods have been established in the last decades for the treatment of injured and degenerated articular cartilage. Osteochondroal transplantation, microfracturing, heat treatment for sealing the surface, shaving, autologous chondrocyte transplantation (ACT), or total joint replacement are among the common techniques applied in today's orthopedic surgery.
Joint replacement techniques where metal, ceramic and/or plastic components are used to substitute partially or totally the damaged or degenerated joint have already a long and quite successful tradition. The use of allograft material has been successful to some extent for small transplants, however, good quality allografts are hardly available.
Osteochondroal transplantation (i.e. mosaicplasty) or autologous chondrocyte transplantation (ACT) are applied whenever total joint replacement is not yet indicated. These methods can be used to treat small and partial defects in a joint. In mosaicplasty defects are filled with osteochondral plugs harvested in non-load bearing areas. In ACT, chondrocytes are harvested by biopsy and grown in-vitro before a highly concentrated cell suspension is injected below an membrane (artificial or autologous) covering the defect area.
Commonly, the replacement of cartilage tissue with solid permanent artificial inserts has been unsatisfactorily because the opposing articular joint surface is damaged by unevenness or by the hardness of the inserts. Therefore, the transplantation technology had to take a step forward in the research of alternative cartilage materials such as biocompatible materials and structures for articular cartilage replacement.
For example, U.S. Pat. No. 5,624,463 describes a prosthetic articular cartilage device comprising a dry, porous volume matrix of biocompatible and at least bioresorbable fibers and a base component. Said matrix establishes a bioresorbable scaffold adapted for the ingrowth of articular chondrocytes and for supporting natural articulating joint forces. Useful fibers include collagen, reticulin, elastin, cellulose, alginic acid, chitosan or synthetic and biosynthetic analogs thereof. Fibers are ordered in substantially circumferentially extending or substantially radially extending orientations. The base component is provided as a support on which the fiber matrix is applied. It is configured to fit in a complementary aperture in defective bone to secure the position of such a device in the bone. The base component is a composite material comprising a dispersion of collagen and composition consisting of tricalcium phosphate and hydroxyapatite.
It has been shown, however, that the function of the above construction has not been always satisfactory. The reason is that said known prosthetic articular cartilage device is frequently unstable due to its structure and thus had to be replaced in the joint area by another surgical operation in to again repair cartilage joints such as knee and hip.
In view of this situation, in the field of articular cartilage replacement materials, there is a need for a structure suitable as a prosthetic articular cartilage which is made of natural resorbable materials or analogs thereof and having an improved structure stability and an accurate positioning in the bone. At the same time, the prosthetic device should be biomechanically able to withstand normal joint forces and to promote repair and replacement of cartilage tissue or cartilage-like tissue.